A phosphor for an electron beam excitation emitting light under an excitation of an electron beam has been conventionally used for a color cathode ray tube, and also used for FED serving as a flat panel display which has been developed recently. As the phosphor for the electron beam excitation used in the color display apparatus such as the color cathode ray tube and the FED, ZnS:Ag, Cl are known as a blue phosphor, and ZnS:Cu, Al are known as a green phosphor. Also, Y2O2S:Eu3+, and Y2O3:Eu3+, YVO4:Eu3+ are known as a red phosphor. Among these phosphors, the Y2O2S:Eu3+ is most generally used in the known color cathode ray tube, for the reason that it has an excellent emission color and exhibits high emission luminance.
In association with a request to the color cathode ray tube of recent years, for a further improved resolution and a high contrast of a display image, an approach is taken to increase an excitation density of the electron beam with which the phosphor is irradiated. However, when the Y2O2S:Eu3+ is used as the red phosphor, even if the excitation density of the electron beam is increased, a phenomenon of a luminance saturation is generated, in which a saturation occurs when the luminance is increased over a fixed value. This is because a temperature quenching phenomenon occurs in the red phosphor by a temperature increase of the phosphor film. Under the saturation phenomenon of the luminance, an emission efficiency of the red phosphor in the color cathode ray tube is deteriorated, thereby also deteriorating an image quality of a display screen during operating of the color cathode ray tube, further involving a problem that chromaticness of white color, which is displayed with a mixed color of RGB, is largely changed by the deterioration of the luminance in red light.
In order to prevent the saturation phenomenon of the luminance, there has been several proposals. For example, according to a non-patent document 1, by slightly adding Tb3+ or Pr3+ to the Y2O2S:Eu3+, the luminance saturation hardly occurs. Also, according to the patent document 1, by adding either of or both of the Tb3+ and Pr3+, and further by slightly adding Ca to the Y2O2S:Eu3+, the luminance is increased. Also, according to the patent document 2, by adding either of or both of the Tb3+ and Pr3+, and further by slightly adding either of or both of Sm and Nd, to the Y2O2S:Eu3+, the luminance is increased.    (Non-patent document 1) “Phosphor handbook” (from page 172 to page 176, Phosphor Research Society, published by Ohmsha, co,. in 1987)    (Patent document 1) Japanese Patent Laid Open No. 2003-13059    (Patent document 2) Japanese Patent Laid Open No. 2000-73053
However, in the cathode ray tube used in a high definition television system and a high resolution computer display and so forth, which are color display apparatus of recent years, in order to attain a further improved resolution and high contrast of the display, a request is made to finely pulverize the phosphor. Along with this, there is an increasing trend of the excitation density of the electron beam, with which the phosphor is irradiated. Therefore, it becomes difficult to obtain a sufficient luminance, because the luminance saturation occurs even when the aforementioned improved Y2O2S:Eu3+ based phosphor is used, involving the problem that a brightness of the screen and a color balance are lost because of an insufficient luminance in the red light, thereby making it difficult to obtain a high quality screen.